"' Relative dating "'is the science of determining the relative order of past events ( i . e ., the age of an object in comparison to another ), without necessarily determining their absolute age, ( i . e . estimated age ).
42.
Since the early years of the twentieth century, absolute dating methods, such as radiometric dating ( including uranium series, and, for very recent fossils, radiocarbon dating ) have been used to verify the relative ages obtained by fossils and to provide absolute ages for many fossils.
43.
The basaltic flows occur on top of continental fluvial and lacustrine sedimentary units of Triassic age . 40 Ar / 39 Ar data ( on plagioclase ) indicate for these basaltic units an absolute age of 198-200 Ma bringing this magmatic event undoubtedly close to the Triassic-Jurassic ( Tr-J ) boundary.
44.
In historical geology, the primary methods of absolute dating involve using the radioactive decay of elements trapped in rocks or minerals, including isotope systems from very young ( radiocarbon dating with ) to systems such as uranium-lead dating that allow acquisition of absolute ages for some of the oldest rocks on earth.
